I'm real big on actually talking to the support before buying. I then judge on how fast they reply, how in-depth the answer is and if I can relate to what they're saying.
Once I've approved them of that, I then look for reviews, background information, etc. The more information I can pull on someone the better. After all, why would I want to be paying someone if I don't even know what they can offer me?
Finally, I'll then look at how they present themselves online. That's another big thing to me. I want to see them making a presence online, and not just staying on their site, doing nothing.